Dual purpose bolometric sensor for heat-assisted magnetic recording device

ABSTRACT

An apparatus comprises a slider and an optical waveguide formed in the slider and configured to receive light from a laser source. A near-field transducer (NFT) is formed on the slider at or near an air bearing surface (ABS) of the slider and optically coupled to the waveguide. A bolometric sensor is positioned proximate the NFT and exposed to at least some of the light. The bolometric sensor is configured to detect changes in output optical power of the laser source and contact between the slider and a magnetic recording medium.

RELATED PATENT DOCUMENTS

This application is a continuation of U.S. patent application Ser. No.15/007,772, filed Jan. 27, 2016, which claims the benefit of ProvisionalPatent Application Ser. No. 62/114,904 filed on Feb. 11, 2015, to whichpriority is claimed pursuant to 35 U.S.C. §119(e), and which areincorporated herein by reference in their entireties.

SUMMARY

Embodiments of the disclosure are directed to an apparatus comprising aslider and an optical waveguide formed in the slider and configured toreceive light from a laser source. A near-field transducer (NFT) isformed on the slider at or near an air bearing surface (ABS) of theslider and optically coupled to the waveguide. A bolometric sensor ispositioned proximate the NFT and exposed to at least some of the light.The bolometric sensor is configured to detect changes in output opticalpower of the laser source and contact between the slider and a magneticrecording medium.

Some embodiments are directed to an apparatus comprising a slider, anoptical waveguide formed in the slider and configured to receive lightfrom a laser source, and a write pole at or near an air bearing surface(ABS) of the slider. A near-field transducer (NFT) is formed on theslider at or near the ABS and optically coupled to the waveguide. TheNFT is positioned adjacent the write pole. A bolometric sensor ispositioned proximate the NFT and exposed to at least some of the light.The bolometric sensor is configured to detect changes in output opticalpower of the laser source and contact between the slider and a magneticrecording medium. The bolometric sensor is situated at or immediatelyadjacent to a thermally actuatable region of the slider that includesthe write pole and the NFT.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a slider in which the variousembodiments disclosed herein may be implemented;

FIG. 2 shows a recording head arrangement in accordance with variousembodiments;

FIG. 3 is a cross-sectional view illustrating portions of a slider bodyproximate a near-field transducer according to a representativeembodiment;

FIG. 4 illustrates a region of a slider which includes a multi-functionsensor situated proximate a near-field transducer in accordance withvarious embodiments;

FIG. 5 illustrates a portion of a magnetic recording medium on which ahotspot has been created by a near-field transducer, such as thenear-field transducer shown in FIG. 4;

FIGS. 6A and 6B illustrate a bolometric sensor situated proximate anear-field transducer in accordance with various embodiments.

FIG. 7A illustrates the portion of the slider shown in FIGS. 6A and 6B,with additional circuitry coupled to the bolometric sensor in accordancewith various embodiments;

FIG. 7B illustrates an embodiment of circuitry which includes adiscriminator that receives signals from a bolometric sensor inaccordance with various embodiments;

FIGS. 8A and 8B illustrate a bolometric sensor situated proximate anear-field transducer in accordance with various embodiments;

FIG. 9 illustrates the portion of the slider shown in FIGS. 8A and 8B,with additional circuitry coupled to the bolometric sensor in accordancewith various embodiments;

FIG. 10 illustrates a bolometric sensor situated proximate a near-fieldtransducer in accordance with various embodiments; and

FIG. 11 illustrates the portion of the slider shown in FIG. 10, withadditional circuitry coupled to the bolometric sensor in accordance withvarious embodiments.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

The present disclosure generally relates to head-to-mediumspacing/contact detection and laser power monitoring in data storagedevices that employ heat-assisted magnetic recording (HAMR), alsoreferred to as energy-assisted magnetic recording (EAMR),thermally-assisted magnetic recording (TAMR), and thermally-assistedrecording (TAR). This technology uses a laser source and a near-fieldtransducer (NFT) to heat a small spot on a magnetic disk duringrecording. The heat lowers magnetic coercivity at the spot, allowing awrite transducer to change the orientation of a magnetic domain at thespot. Due to the relatively high coercivity of the medium after cooling,the data is less susceptible to paramagnetic effects that can lead todata errors.

Generally, recording heads may utilize heaters for fine control ofhead-to media spacing. The heaters heat a portion of the recording headthat faces a recording medium. The heating causes a local protrusion dueto thermal expansion of the material. Thermal protrusion can be finelycontrolled to maintain a desired clearance between read/writetransducers and the recording medium. The regions subject to thermalprotrusion control typically include a region proximate the writer and,in some implementations, a region proximate the reader. Each of theseregions, when thermally activated, becomes a so-called close pointrelative to the recording medium.

In order to establish an appropriate or optimal dynamic clearance forthe read/write transducer, it is desirable to measure fly height at theclose point or points, since these regions are closest to the recordingmedium when thermally actuated. Further, while conventional read/writetransducers may be allowed to contact the recording medium under someconditions, a HAMR device may be damaged if such contact occurs whilerecording. This can make the estimation and control of head-to-mediumspacing (e.g., dynamic clearance) more difficult in a HAMR recordinghead. The introduction of optical components to the read/writetransducer in HAMR devices, however, complicates head-to-medium spacingand contact detection due to the physical presence and heat generated bythe optical components.

For example, in HAMR recording transducers, the location of a fly heightsensor is restricted to areas outside of the optical path in order toensure light delivery to the NFT is not degraded by the presence of thefly height sensor. Ideally, any sensor designed for head-diskinteraction would be at the close point of the recording transducer,which for current HAMR transducers is preferably at the NFT and writepole. However, due to the requirement that the fly height sensor mustnot compromise light delivery, fly height sensors are typically spacedmore than 1 μm from the NFT and write pole.

A HAMR drive generally uses a laser diode to heat the recording mediumto aid in the recording process. The laser diode generates heat and isalso heated by other components (writer, reader, heater elements) in themagnetic slider. During write operation, for example, laser diodeheating can vary the junction temperature of the laser diode, causing ashift in laser emission wavelength, leading to a change of opticalfeedback from optical path in slider to the cavity of the laser diode, aphenomenon that is known to lead to mode hopping/power instability ofthe laser diode. Mode hopping is particularly problematic in the contextof single-frequency lasers. Under some external influences, asingle-frequency laser may operate on one resonator mode (e.g., produceenergy with a first wavelength) for some time, but then suddenly switchto another mode (produce energy, often with different magnitude, with asecond wavelength) performing “mode hopping.” Temperature variation isknown to cause mode hopping in laser diodes. Mode hopping is problematicfor HAMR applications, as mode hopping leads to laser output powerjumping and magnetic transition shifting from one block of data toanother. Large transition shifts in a block of data may not berecoverable by channel decoding, resulting in error bits.

Monitoring of laser power is important to ensure proper operation of thelaser diode and to avoid instabilities such as mode hopping.Conventional laser power monitoring involves use of an externalphotodiode situated on a submount that also supports the laser diode.The photodiode senses optical power output of the laser diode, and canbe used to determine if the laser performance is sufficiently stable toensure adequate writing performance. However, future integrated HAMRrecording transducers will not be able to include an external photodiodedue to reduced submount dimensions.

Adequate head-medium contact detection response remains critical to harddrive development. For HAMR hard drives, it is also critical to detectsmall fluctuations in laser output optical power delivered to the NFTwhile minimizing any light delivery losses. Typically, an electricalelement such as an internal laser power monitor (e.g., photodiode) wouldrequire extra, dedicated electrical bond pads. Since additional bondpads add cost and complexity to the head gimbal assembly, it isdesirable to provide both sensing of head-medium interactions and laseroutput optical power without the need for additional bond pads.

Embodiments of the disclosure are directed to a sensor arrangement thatcan be used to detect head-to-medium spacing and contact and, inaddition, be used to monitor output optical power of the laser diode.Embodiments are directed to a single sensor that can perform the dualfunctions of sensing head-to-medium spacing/contact and output opticalpower of the laser diode. Embodiments are directed to a dual functionsensor that can be situated at or immediately adjacent the writer closepoint. Embodiments of the disclosure are directed to a dual functionsensor that can be situated in the light path of the slider yet havesubstantially no or only negligible impact on performance of thenear-field transducer. Embodiments are directed to a dual functionsensor that can harvest waste light that would otherwise exit the sliderand improve compactness of the heated spot created on the magnetic disk.Embodiments are directed to a dual function sensor implemented as asingle, unified device that requires only one set of electrical bondpads, does not degrade light path efficiency due to its locationdownstream of the NFT, and demonstrates unique approaches to crossingthe light path either through a series connection via existingelectrically conductive structures or by forming out-and-backgeometries.

According to various embodiments, a bolometric sensor can be situatedadjacent the near-field transducer so that light produced by the laserdiode impinges on the bolometric sensor. The bolometric sensor can besituated in or near the optical light path of the slider so that itabsorbs waste light that would otherwise exit the slider and causeunwanted heating of the magnetic disk adjacent the hotspot created bythe near-field transducer. In various embodiments, the bolometric sensorcomprises a thin metallic element with a high thermal coefficient ofresistance (TCR) that is embedded in the slider of a read/writetransducer near the optical light path. The bolometric sensor ispreferably situated at or near the air bearing surface (ABS) of theslider so that it can sense for changes in temperature resulting fromchanges in head-to-medium spacing and contact.

When a small bias current is applied across the bolometric sensor, anychange in bolometric sensor temperature will create a correspondingchange in measured voltage. As a result, the bolometric sensor can beused to monitor head-medium interactions due to the fact that the ABSheat transfer coefficient changes as a read/write transducer approachesa spinning disk. The bolometric sensor can also be used to monitorfluctuations in laser output optical power that cause fluctuations inabsorption and temperature in the bolometric sensor. In general, abolometer-based internal power monitor must not decrease light pathefficiency while still absorbing enough light to create a sufficientlylarge signal for detection. Moreover, it is desirable that thebolometric sensor not require any additional bond pads and would ideallybe wired in series or parallel with an existing sensor of the recordingtransducer. A bolometric sensor of the present disclosure can beimplemented as a single device that can be used for both head-mediumcontact detection and laser power monitoring, that maintains extremeproximity to the mechanical close point, and does not in any significantway degrade the light path or optics.

Referring now to FIG. 1, a block diagram shows a side view of aread/write transducer 102 according to a representative embodiment. Theread/write transducer 102 may be used in a magnetic data storage device,e.g., hard drive. The read/write transducer 102 may also be referred toherein as a slider, read head, recording head, etc. The read/writetransducer 102 is coupled to an arm 104 by way of a suspension 106 thatallows some relative motion between the read/write transducer 102 andarm 104. The read/write transducer 102 includes read/write transducers108 at a trailing edge that are held proximate to a surface 110 of amagnetic recording medium 111, e.g., magnetic disk. The read/writetransducer 102 is configured as a HAMR recording head, which includes alaser 120 (or other energy source) and a waveguide 122. The waveguide122 delivers light from the laser 120 to components near the read/writetransducers 108.

When the read/write transducer 102 is located over surface 110 ofrecording medium 111, a flying height 112 is maintained between theread/write transducer 102 and the surface 110 by a downward force of arm104. This downward force is counterbalanced by an air cushion thatexists between the surface 110 and an air bearing surface 103 (alsoreferred to herein as a “media-facing surface”) of the read/writetransducer 102 when the recording medium 111 is rotating. It isdesirable to maintain a predetermined slider flying height 112 over arange of disk rotational speeds during both reading and writingoperations to ensure consistent performance. Region 114 is a “closepoint” of the read/write transducer 102, which is generally understoodto be the closest spacing between the read/write transducers 108 and themagnetic recording medium 111, and generally defines the head-to-mediumspacing 113. To account for both static and dynamic variations that mayaffect slider flying height 112, the read/write transducer 102 may beconfigured such that a region 114 of the read/write transducer 102 canbe configurably adjusted during operation in order to finely adjust thehead-to-medium spacing 113. This is shown in FIG. 1 by a dotted linethat represents a change in geometry of the region 114. In this example,the geometry change may be induced, in whole or in part, by an increaseor decrease in temperature of the region 114 via a heater 116.

FIG. 2 shows a recording head arrangement 200 in accordance with variousembodiments. The recording head arrangement 200 includes a slider 202positioned proximate a rotating magnetic medium 211. The slider 202includes a reader 204 and a writer 206 proximate the ABS 215 forrespectively reading and writing data from/to the magnetic medium 211.The writer 206 is located adjacent an NFT 210 which is optically coupledto a light source 220 (e.g., laser diode) via a waveguide 222. The lightsource 220 can be mounted external, or integral, to the slider 202. Thelight source 220 energizes the NFT 210 via the waveguide 222. The writer206 includes a corresponding heater 207, and the reader 204 includes acorresponding heater 205 according to various embodiments. The writerheater 207 can be powered to cause protrusion of the ABS 215predominately in the ABS region at or proximate the writer 206, and thereader heater 205 can be powered to cause protrusion of the ABS 215predominately in the ABS region at or proximate the reader 204. Powercan be controllably delivered independently to the heaters 207 and 205to adjust the fly height (e.g., clearance) of the slider 202 relative tothe surface of the recording medium 211.

In FIG. 3, a cross-sectional view illustrates portions of the sliderbody 301 near the near-field transducer 312 according to arepresentative embodiment. In this view, the NFT 312 is shown proximatethe ABS 308 of the slider body 301 and to a surface of magneticrecording medium 307, e.g., a magnetic disk. The NFT 312 shown in FIG. 3is of an NTS (near-field transducer stadium style) design which includesan enlarged region having a sloped planar upper surface. It is notedthat NFT 312 can be of a different design, such as a so-called lollipopor peg-only (e.g., nanorod) design, for example. A peg 318 extends fromthe lower portion enlarged region and terminates near or at the ABS 318.A waveguide 305 delivers electromagnetic energy from a laser diode(e.g., see laser 120 in FIG. 1) to the near-field transducer 312, whichdirects the energy to create a small hotspot 309 on the recording medium307. The waveguide 305 comprises a layer of core material 310surrounding by cladding layers 312 and 314. A magnetic write pole 306causes changes in magnetic flux near the media facing surface 308 inresponse to an applied current. Flux from the write pole 306 changes amagnetic orientation of the hotspot 309 as it moves past the write pole306 in the downtrack direction (z-direction). FIG. 3 also shows abolometric sensor 330 situated at the ABS 308 adjacent to, but spacedapart from, the NFT 312.

Turning now to FIG. 4, there is illustrated a region 400 of a sliderwhich includes a multi-function sensor 420 situated proximate an NFT 410in accordance with various embodiments. The region 400 of the slidershown in FIG. 4 includes structure 402 surrounding the NFT 410, whichincludes a diffuser region 404 and heat channel regions 406 that can bemade out of electrically conductive material. The NFT 410 includes a peg411 positioned at or near the ABS 405 of the slider. A bolometric sensor420 is situated at the ABS 405 and positioned in a spaced-apartrelationship with respect to the NFT 410. In the illustrative exampleshown in FIG. 4, the bolometric sensor 420 includes a first bolometricsensor 422 and a second bolometric sensor 422, each of which is spacedfrom a centerline 405 of the NFT 410 by a distance, d1. All or at leasta portion of the first and second bolometric sensors 422 and 424 extendsinto the optical path so that light produced by the laser diode impingeson the first and second bolometric sensors 422 and 424. The first andsecond bolometric sensors 422 and 424 are positioned on the slider sothat laser light impinging on the sensors 422 and 424 is waste lightthat would otherwise exit the ABS 405.

The first and second bolometric sensors 422 and 424 approach thecenterline 405 of the NFT 410 from opposing directions along the ABS 405and terminate at a distance d1 spaced from the centerline 405. Asdiscussed above, the terminal ends of the first and second bolometricsensors 422 and 424 are spaced apart from the NFT 410 so as to absorbwaste light that would otherwise exit the slider and impinge on thesurface of the adjacent magnetic recording medium. Importantly, thefirst and second bolometric sensors 422 and 424 are positioned relativeto the NFT 410 so that the sensors 422 and 424 do not degrade the lightpath or optics within the slider. In this regard, the first and secondbolometric sensors 422 and 424 have no or only a negligible impact onthe performance of the NFT 410. For example, the first and secondbolometric sensors 422 and 424 can be positioned relative to the NFT 410so that only a small increase (e.g., 5% or less) in the temperature atthe peg 411 of the NFT 410 results, if at all.

According to various embodiments, the terminal ends of the first andsecond bolometric sensors 422 and 424 can be spaced apart from thecenterline 405 of the NFT 410 by a distance, d1, of between about 350 nmand 1 μm. In some embodiments, the terminal ends of the first and secondbolometric sensors 422 and 424 can be spaced apart from the centerline405 of the NFT 410 by a distance, d1, of between about 500 nm and 1 μm.In other embodiments, the terminal ends of the first and secondbolometric sensors 422 and 424 can be spaced apart from the centerline405 of the NFT 410 by a distance, d1, of between about 350 nm and 500nm. Positioning the first and second bolometric sensors 422 and 424 in aspaced relationship with respect to the NFT 410 on the order of betweenabout 350 nm and 1 μm provides sufficient absorption of light to createa sufficiently large signal for detecting laser output optical power andchanges thereof, with no or only negligible adverse impact on NFTperformance. A bias current on the order of 1 mA is expected to producea detectable voltage drop associated with a 1% fluctuation in laseroutput optical power.

Positioning the bolometric sensor 420 in close proximity to the NFT 410provides for sensing of fly height changes of the slider at orimmediately adjacent the write close point of the slider. Because thebolometric sensor 420 is positioned immediately adjacent the NFT 410,and because the NFT 410 and is positioned immediately adjacent the writepole (e.g., within about 10 to 100 nm), the dual function bolometricsensor 420 can provide for highly accurate fly height measurements forthe write close point of the slider.

FIG. 5 illustrates a portion of a magnetic recording medium 501 on whicha hotspot 500 has been created by an NFT, such as NFT 410 shown in FIG.4. The hotspot 500 includes a primary hotspot 502 created by the peg 411of the NFT 410 shown in FIG. 4. Surrounding the primary hotspot 502 is asecondary hotspot 504 created by waste light exiting the ABS 405 nearthe NFT 410. The waste light emanating from the ABS 405 causesbackground heating of the medium adjacent the primary hotspot 502. Thisbackground heating of the medium 501 causes undesirable enlargement ofthe primary hotspot 502 beyond desired dimensions of the primary hotspot502. Enlargement of the primary hotspot 502 beyond desired dimensionscan result in unintended heating of and writing to/erasure of mediumlocations adjacent the primary hotspot 502 (e.g., such as neighboringmagnetic domains or bits). The bolometric sensor 420 advantageouslyharvests waste light that would otherwise result in background heatingof the recording medium surrounding the primary hotspot 502. As aresult, the enlarged region 504 adjacent the primary hotspot 502 issignificantly reduced in size (to that of region 506, for example) dueto absorption of waste light by the bolometric sensor 420.

FIGS. 6A and 6B illustrate a region 600 of a slider that includes abolometric sensor 620 situated proximate an NFT 610 in accordance withvarious embodiments. FIG. 6A is a simplified view of the slider region600 which excludes the write pole for purposes of clarity ofillustration. FIG. 6B is a perspective view of the slider region 600which includes the write pole 615 proximate an NFT 610. The NFT 610 isshown as a stadium-style near-field transducer, it being understood thata lollipop, nanorod, or other NFT configuration can be used. The portion600 of the slider shown in FIGS. 6A and 6B is similar to that shown inFIG. 4, and includes a diffuser region 604 and heat channel regions 606.The bolometric sensor 620 is shown to include a pair of wire sensors 622and 624 formed from a metal having a relatively high TCR. Suitablemetals include W, Ru, Cr, NiFe, etc. Generally, a TCR value of 1.5e-3°C.⁻¹ or higher is preferred, although operating conditions can bechanged to accommodate a lower TCR value. That is, the measurable signalis proportional to the bias current times the TCR times the change intemperature times the intrinsic resistance of the sensor (I*TCR*dT*R₀)such that a slightly higher bias current can be applied or a higherintrinsic resistance can be designed to compensate for a lower TCR.

In the embodiment shown in FIGS. 6A and 6B, a first wire sensor 622extends between an electrical lead 625 and a first via 632. A secondwire sensor 624 extends between an electrical lead 627 and a second via634. The first and second wire sensors 622 and 624 extend along the ABS605 of the slider. The first and second vias 632 and 634 defineelectrically conductive pathways to structures of the slider surroundingthe NFT 610 and situated away from the ABS 605. In particular, the firstand second vias 632 and 634 extend to electrically conductive structures640 (e.g., Au structures) proximate the NFT 610 that allow current totravel (as indicated by arrows) between the first and second vias 632and 634. In this regard, the bolometric sensor 620 has a bridgedconfiguration, since part of the slider structure provides anelectrically conductive bridge that electrically couples the first andsecond wire sensors 622 and 624. As such, an electrically conductivecircuit is formed between the first wire sensor 622, the first via 632,the electrically conductive structure pathway 640, the second via 634,and the second wire sensor 624.

The first and second wire sensors 622 and 624 are respectively connectedto first and second electrical leads 625 and 627, which are connected toelectrical bond pads of the recording transducer as will be describedbelow. The first and second wire sensors 622 and 624 can have a lengthof about 1 to 10 μm. The first and second leads 625 and 627 arepreferably formed from a material having a low or zero TCR. However, solong as the intrinsic resistance (R₀) of the leads is much smaller thanthat of the sensor, a low or zero TCR material may not be necessary.Other sections of the electrical circuit in addition to the first andsecond leads 625 and 627 are preferably formed from a low or zero TCRmaterial. Use of low or zero TCR electrical leads and/or electricalleads with low intrinsic resistance insures that signals generated bythe first and second wire sensors 622 and 624 are largely or entirelydue to temperature changes in the vicinity of the NFT 610, and not fromneighboring structures of the slider.

FIG. 7A illustrates the portion 600 of the slider shown in FIGS. 6A and6B with additional circuitry coupled to the bolometric sensor 620 inaccordance with various embodiments. The electrical circuit shown inFIG. 7A includes the first wire sensor 622 connected to the first lead625, and the first lead 625 coupled to a first bond pad 702. The secondwire sensor 624 is shown connected to the second lead 627, and thesecond lead 627 is shown coupled to a second bond pad 704. The first andsecond bond pad 702 and 704 are respectively coupled to bias sources(not shown) and to circuitry 706 via conductors 722 and 732respectively. The first and second bond pads 702 and 704 can be bondpads designated for a fly height or contact sensor, for example.Provision of a dual function bolometric sensor 620 allows a single pairof bond pads to be used for a single sensor that performs both flyheight sensing/contact detection and laser output optical powermonitoring, thereby obviating the need for a second pair of bond pads(e.g., one pair of bond pads for contact detection sensor and a secondpair of bond pads for laser power monitoring).

In some embodiments, a single pair of bond pads 702 and 704 can beshared between different components of the recording transducer. Forexample, the bond pads 702 and 704 can be connected to the reader and tothe bolometric sensor 620 (with other components as appropriate). Sincethe reader need not be powered during write operations, the bolometricsensor 620 can be active when reading is not occurring, such as duringwrite operations when the NFT 610 is active. Laser power monitoringand/or fly height measurements/contact detection can be conducted duringperiods when the reader is not active, for example.

The circuitry 706 is configured to communicate a signal 708 indicativeof slider flying height/contact and/or laser output optical power andchanges thereof to other electrical or electronic components of the harddrive (e.g., a processor or controller). In some embodiments, fly heightmeasurements and contact detection can occur at times when laser powermonitoring is not being conducted, and vice versa. Performing thesemeasurements at different times allows for easy determination as to theorigin of the signals produced by the circuitry 706. In someembodiments, fly height measurements/contact detection and laser powermonitoring can be conducted at the same time, and the circuitry 706 canbe configured to discriminate between signals produced from fly heightmeasurements/contact detection and those produced from laser powermonitoring.

FIG. 7B illustrates an embodiment of circuitry 706 which includes adiscriminator 752 that receives signals from the bolometric sensor 620.The discriminator 752 is configured to discriminate signals produced bythe bolometric sensor 620 when performing laser power monitoring andwhen performing fly height and contact detection measurements. Thediscriminator 752 can perform discrimination of both signal typesconcurrently or sequentially. Typically, the bolometric sensor signalhas relatively high frequency components when performing laser powermonitoring, and relatively low-frequency components when performing flyheight and contact detection measurements. For example, the bolometricsensor signal can have frequency components in the megahertz range whenperforming laser power monitoring, and frequency components in thekilohertz range or lower when performing fly height and contactdetection measurements. The discriminator 752 can include a high pass orbandpass filter for extracting bolometric sensor signal contentassociated with laser power monitoring. The discriminator 752 caninclude a low pass or bandpass filter for extracting bolometric sensorsignal content associated with fly height and contact detectionmeasurements. In some implementations, the discriminator 752 can includea detector configured to detect amplitude spikes in the bolometricsensor signal indicative of contact between the slider and the recordingmedium.

FIGS. 8A and 8B illustrate a region 800 of a slider that includes abolometric sensor 820 situated proximate an NFT 610 in accordance withvarious embodiments. FIG. 8A is a simplified view of the slider region600 which excludes the write pole for purposes of clarity ofillustration. FIG. 8B is a perspective view of the slider region 600which includes the write pole 615 proximate an NFT 610. The NFT 610 isshown as a stadium-style near-field transducer for purposes ofillustration and not of limitation. The portion 800 of the slider shownin FIGS. 8A and 8B is similar to that shown in FIGS. 4-7, and includes adiffuser region 604 and heat channel regions 606. The bolometric sensor820 shown in FIGS. 8A and 8B has a hairpin configuration (e.g.,elongated looped configuration forming a hairpin), comprising first andsecond wire sensors 820′ and 820″ that approach the NFT 610 fromopposing directions and turn back on themselves to form a pair ofhairpin sensors. At a location away from the ABS 605 and out of theoptical path, these two hairpin shaped wire sensors 820′ and 820″ can beconnected in series or parallel with each other.

The first and second wire sensors 820′ and 820″ are preferably formedfrom a metal having a relatively high TCR. The first sensor wire 820′includes a first wire 822 spaced apart and arranged in parallel with asecond wire 823. The first and second wires 822 and 823 can be spacedapart from one another by about 150 nm (i.e. have a pitch, d2, of 150nm). The first and second wires 822 and 823 of the first wire sensor 820are respectively connected to first and second electrical leads 827 and828. The second sensor wire 820″ includes a first wire 824 spaced apartand arranged in parallel with a second wire 825. The first and secondwires 824 and 825 can be spaced apart from one another by about 150 nm.The first and second wires 824 and 825 are respectively connected tofirst and second electrical leads 829 and 830. The wires 822-825 of thefirst and second wire sensors 820′ and 820″ can have a length of about 1to 10 μm. The electrical leads 827-830 are preferably formed from amaterial having a low or zero TCR. Other sections of the electricalcircuit in addition to the electrical leads 827-830 are preferablyformed from a low or zero TCR material.

FIG. 9 illustrates the portion 800 of the slider shown in FIGS. 8A and8B with additional circuitry coupled to the bolometric sensor 820 inaccordance with various embodiments. The electrical circuit shown inFIG. 9 includes first and second wires 822 and 823 of a first wiresensor 820′ respectively connected to first and second leads 827 and828. The electrical circuit also includes first and second wires 824 and825 of a second wire sensor 820″ respectively connected to first andsecond leads 829 and 830. The first lead 827 couples the first wiresensor 820′ to electrical bond pad 902, and the first lead 829 couplesthe second wire sensor 820″ to the electrical bond pad 904. The firstand second wire sensors 820′ and 820″ are coupled in series viaconductor 940 respectively connected to second leads 828 and 830.Circuitry 906 is coupled to the first and second bond pads 902 and 904via conductors 922 and 932, respectively.

The circuitry 906 is configured to communicate a signal 908 indicativeof slider flying height/contact and/or laser output optical power andchanges thereof to other electrical or electronic components of the harddrive. In some embodiments, fly height measurements and contactdetection can occur at times when laser power monitoring is not beingconducted, and vice versa. In some embodiments, the circuitry 906 can beconfigured to discriminate between signals produced from fly heightmeasurements/contact detection and those produced from the laser powermonitoring in a manner previously discussed. The bolometric sensors 820′and 820″ can be connected to bond pads 902 and 904 exclusively or in abond pad sharing relationship with one or more other components of therecording transducer.

FIG. 10 illustrates a region 1000 of a slider that includes a bolometricsensor 1020 situated proximate an NFT 610 in accordance with variousembodiments. The NFT 610 is shown as a stadium-style near-fieldtransducer for purposes of illustration and not of limitation. Theportion 1000 of the slider shown in FIG. 10 is similar to that shown inFIGS. 4-9, and includes a diffuser region 604 and heat channel regions606. The bolometric sensor 1020 shown in FIG. 10 has a wishboneconfiguration (e.g., elongated looped configuration forming a wishbone),comprising first and second wire sensors 1020′ and 1020″ that approachthe NFT 610 from opposing directions and turn back on themselves to forma pair of wishbone shaped sensors. The wishbone sensor configuration issimilar to the hairpin configuration shown in FIGS. 8 and 9, but mayease required critical dimensions. At a location away from the ABS 605and out of the optical path, these two wishbone shaped wire sensors1020′ and 1020″ can be connected in series or parallel with each other.

The first and second wire sensors 1020′ and 1020″ are preferably formedfrom a metal having a relatively high TCR. The first sensor wire 1020′includes a first wire 1022 spaced apart and arranged at an acute angle(e.g., less than 45°) with respect to a second wire 1023. The first andsecond wires 1022 and 1023 can be spaced apart from one another by atleast 150 nm as a minimum dimension. The first and second wires 1022 and1023 of the first wire sensor 1020′ are respectively connected to firstand second electrical leads 1027 and 1028. The second sensor wire 1020″includes a first wire 1024 spaced apart and arranged at an acute angle(e.g., less than 45°) with respect to a second wire 1025. The first andsecond wires 1024 and 1025 can be spaced apart from one another by about150 nm as a minimum dimension. The first and second wires 1024 and 1025are respectively connected to first and second electrical leads 1029 and1030. The wires 1022-1025 of the first and second wire sensors 1020′ and1020″ can have a length of about 1 to 10 μm. The electrical leads1027-1030 are preferably formed from a material having a low or zeroTCR. Other sections of the electrical circuit in addition to theelectrical leads 1027-1030 are preferably formed from a low or zero TCRmaterial.

FIG. 11 illustrates the portion 1000 of the slider shown in FIG. 10 withadditional circuitry coupled to the bolometric sensor 1020 in accordancewith various embodiments. The electrical circuit shown in FIG. 11includes first and second wires 1022 and 1023 of the first wire sensor1020′ respectively connected to first and second leads 1027 and 1028.The electrical circuit also includes first and second wires 1024 and1025 of the second wire sensor 1020″ respectively connected to first andsecond leads 1029 and 1030. The first lead 1027 couples the first wiresensor 1020′ to electrical bond pad 1102, and the first lead 1029couples the second wire sensor 1020″ to the electrical bond pad 1104.The first and second wire sensors 1020′ and 1020″ are coupled in seriesvia conductor 1140 respectively connected to second leads 1028 and 1030.Circuitry 1106 is coupled to the first and second bond pads 1102 and1104 via conductors 1122 and 1132, respectively.

The circuitry 1106 is configured to communicate a signal 1108 indicativeof slider flying height/contact and/or laser output optical power andchanges thereof to other electrical or electronic components of the harddrive. In some embodiments, fly height measurements and contactdetection can occur at times when laser power monitoring is not beingconducted, and vice versa. In some embodiments, the circuitry 1106 canbe configured to discriminate between signals produced from fly heightmeasurements/contact detection and those produced from the laser powermonitoring in a manner previously discussed. The bolometric sensors1020′ and 1020″ can be connected to bond pads 1102 and 1104 exclusivelyor in a bond pad sharing relationship with one or more other componentsof the recording transducer.

All of the aforementioned designs can improve proximity of a bolometricsensor relative to the NFT and write pole over conventionalimplementations. In addition, positioning of the bolometric sensorproximate the light path at the ABS allows the bolometric sensor toabsorb wasted light that would otherwise exit the ABS and broaden themedia thermal profile. Modeling has produced laser-induced headtemperature contours demonstrating that bolometric sensor temperature isdependent on the incident laser output optical power, though thepresence of the bolometric sensor does not significantly affect NFTtemperature.

Systems, devices or methods disclosed herein may include one or more ofthe features structures, methods, or combination thereof describedherein. For example, a device or method may be implemented to includeone or more of the features and/or processes above. It is intended thatsuch device or method need not include all of the features and/orprocesses described herein, but may be implemented to include selectedfeatures and/or processes that provide useful structures and/orfunctionality.

Various modifications and additions can be made to the disclosedembodiments discussed above. Accordingly, the scope of the presentdisclosure should not be limited by the particular embodiments describedabove, but should be defined only by the claims set forth below andequivalents thereof.

What is claimed is:
 1. An apparatus, comprising: a slider configured forheat-assisted magnetic recording; an optical waveguide formed in theslider and configured to receive light from a laser source; a near-fieldtransducer (NFT) formed on the slider at or near an air bearing surface(ABS) of the slider and optically coupled to the waveguide; a writeradjacent the NFT; and a bolometric sensor positioned at or near a writerclose point and exposed to at least some of the light, the bolometricsensor configured to detect changes in output optical power of the lasersource, changes in spacing between the slider and a magnetic recordingmedium, and contact between the slider and the recording medium.
 2. Theapparatus of claim 1, wherein the bolometric sensor is coupled to asingle pair of electrical bond pads of the slider.
 3. The apparatus ofclaim 1, wherein the bolometric sensor is coupled to a single pair ofelectrical bond pads of the slider and to at least one other componentof the slider.
 4. The apparatus of claim 3, wherein the at least oneother component comprises a reader.
 5. The apparatus of claim 1, whereinthe bolometric sensor is configured to concurrently detect changes inoutput optical power of the laser source, changes in spacing between theslider and the recording medium, and contact between the slider and therecording medium.
 6. The apparatus of claim 1, wherein the bolometricsensor is configured to: detect changes in output optical power of thelaser source during a first mode; and detect contact and spacing changesbetween the slider and the recording medium during a second mode.
 7. Theapparatus of claim 1, wherein the bolometric sensor is configured to:produce a first output signal indicative of contact and spacing changesbetween the slider and the recording medium; and produce a second outputsignal indicative of output optical power of the laser source; and theapparatus comprises circuitry coupled to the bolometric sensor andconfigured to discriminate between the first output signal and thesecond output signal.
 8. The apparatus of claim 1, wherein the lightimpinging on the bolometric sensor comprises light that would otherwiseexit the ABS as wasted light.
 9. The apparatus of claim 1, whereinexposure of the light on the bolometric sensor has a negligible effecton NFT temperature.
 10. The apparatus of claim 1, wherein the bolometricsensor is configured to reduce background heating of the recordingmedium proximate the apparatus relative to the apparatus lacking thebolometric sensor.
 11. An apparatus, comprising: a slider configured forheat-assisted magnetic recording; an optical waveguide formed in theslider and configured to receive light from a laser source; a write poleat or near an air bearing surface (ABS) of the slider; a near-fieldtransducer (NFT) formed on the slider at or near the ABS and opticallycoupled to the waveguide, the NFT positioned adjacent the write pole;and a bolometric sensor positioned at or near the ABS so as to beexposed to light that would otherwise exit the ABS as wasted light, thebolometric sensor configured to detect changes in output optical powerof the laser source, changes in spacing between the slider and amagnetic recording medium, and contact between the slider and therecording medium.
 12. The apparatus of claim 11, wherein the bolometricsensor is situated at or immediately adjacent to a thermally actuatableregion of the slider that includes the write pole and the NFT.
 13. Theapparatus of claim 11, further comprising circuitry coupled to thebolometric sensor, the circuitry configured to detect a change involtage or current corresponding to a change in temperature resultingfrom the changes in output optical power the changes in spacing andcontact between the slider and the recording medium.
 14. The apparatusof claim 11, wherein the bolometric sensor is coupled to a single pairof electrical bond pads of the slider.
 15. The apparatus of claim 11,wherein the bolometric sensor is coupled to a single pair of electricalbond pads of the slider and to at least one other component of theslider.
 16. The apparatus of claim 11, wherein the bolometric sensor isconfigured to concurrently detect changes in output optical power of thelaser source, changes in spacing between the slider and the recordingmedium, and contact between the slider and the recording medium.
 17. Theapparatus of claim 11, wherein the bolometric sensor is configured to:detect changes in output optical power of the laser source during afirst mode; and detect contact and spacing changes between the sliderand the recording medium during a second mode.
 18. The apparatus ofclaim 11, wherein the bolometric sensor is configured to: produce afirst output signal indicative of contact and spacing changes betweenthe slider and the recording medium; and produce a second output signalindicative of output optical power of the laser source; and theapparatus comprises circuitry coupled to the bolometric sensor andconfigured to discriminate between the first output signal and thesecond output signal.
 19. A method, comprising: providing relativemovement between a magnetic recording medium and a slider configured forheat-assisted magnetic recording; thermally actuating a region of theslider that includes a write pole and a near-field transducer (NFT);sensing, using a bolometric sensor positioned at or near the thermallyactuated region, changes in output optical power of a laser source andchanges in spacing between the slider and the recording medium; anddetecting contact between the slider and the recording medium using thebolometric sensor.
 20. The method of claim 19, comprising: producing, bythe sensor, a first output signal indicative of contact and spacingchanges between the slider and the recording medium; producing, by thesensor, a second output signal indicative of output optical power of thelaser source; and discriminating between the first output signal and thesecond output signal.